Install devstack requirements as part of the course_discovery Docker build

docker/build/course_discovery/Dockerfile

@@ -21,7 +21,7 @@ WORKDIR /edx/app/edx_ansible/edx_ansible/docker/plays
 COPY docker/build/course_discovery/ansible_overrides.yml /
 RUN sudo ansible-playbook course_discovery.yml \
     -c local -i '127.0.0.1,' \
-    -t 'install,assets' \
+    -t 'install,assets,devstack:install' \
     --extra-vars="@/ansible_overrides.yml" \
     --extra-vars="COURSE_DISCOVERY_VERSION=$COURSE_DISCOVERY_VERSION" \
     --extra-vars="COMMON_GIT_PATH=$REPO_OWNER"